Currently, most smart TVs support that multiple display windows display different contents (e.g. Picture In Picture (PIP) or Picture Out Picture (POP)) in their screens, when switching between a main display window and a sub-display window, the TV mainly has the following switching methods:
In the case that two different TV programs are received from the same program source (e.g. all parsed from the TV program stream of the broadcast system), before switching, the TV parses, from the received TV program streams, the TV programs of the corresponding channels displayed in the main display window and the sub-display window respectively, and displays the respective contents through the main display window and the sub-display window, when the switching is executed, the TV operates the two parsed contents displayed by the windows of each other. Currently, in the case that two different programs are received from different program sources, such as receiving the TV program stream from the broadcast system and also receiving the programs from the server of the Internet, before switching, the TV parses, from the received TV program signals, the program displayed in the main window, and receives, from the server, the program data displayed in the sub-display window, and then displays the respective contents through the main display window and the sub-display window. When the switching is executed, the TV controls the two content portions to be displayed using the windows of the other party.
The said switching process of the TV display windows is achieved by the TV device, and it does not need to make any change to the process of receiving signals. For example, the description of China patent application No. CN200880016617 publicizes that the display is capable of receiving one or more TV channels and an independent designated application channel and having at least a first display window and a second display window. The information sent by the designated application channel is displayed on the first display window while simultaneously one of the TV channels is displayed on the second display window, and the information received from the designated application channel is allowed to switch between the first display window and the second display window.
As the first display window and the second display window normally corresponds to the main display window with big size and the sub-display window with small size, and after switching, if the low resolution content displayed in the sub-display window originally is enlarged to be displayed in the main display window, the display quality will be reduced significantly as a result.